Rabbi, I’m a 12-year-old American who does not keep Kosher. My grandfather and uncle wish for me to have a Bat Mitzvah. Would this be a disgrace to G-d?

If you are Jewish- in other words if your mother is Jewish- the more of G-d's commandments (=mitzvot) that you keep, the better. The fact that you do not yet keep kosher does not mean that you should not observe other mitzvot. Together with your grandfather and your uncle, you should arrange to speak with an Orthodox rabbi in your area, to ensure that the Bat- Mitzva you will be celebrating will be conducted according to Jewish law and custom and without desecration of the Sabbath. Mazal Tov!